The present invention relates generally to load carrying devices. More particularly, it relates to shock absorbing devices of the type which are mounted to vehicles and which use both an elastomeric spring and a selectively pressurizable chamber for absorbing shock, energy dissipation and carrying or leveling load. However, it will be appreciated by those skilled in the art that the invention can be readily adapted for use in other environments as, for example, where similar spring damping devices are employed to protect or cushion other items.
Known dry viscous spring damper devices of the type described have included elastomeric shear springs, elastomeric diaphragms, selectively pressurizable gas chambers and subchambers including elastomeric composite particles or fluid. Such a dry viscous spring damper device is described in application Ser. No. 436,331, filed Oct. 25, 1982 in the name of Shtarkman and assigned to the assignee of the subject application. In the Shtarkman application, a dry viscous spring damper is provided which is comprised of a first housing member joined to a second housing member with an elastomeric shear spring. A first chamber in the damper is separated from a second chamber in the damper by an elastomeric diaphragm. A valve is provided for selectively pressurizing the second chamber with pressurized gas or air. A plurality of elastomeric particles are included in the first chamber whereby relative movement between the housing members operates to stress the shear spring and the elastomeric particles and vary the volumes of the first and second chambers.
A particular problem with viscous spring dampers is the lack of effective control over the form of deformation of the elastomeric springs of such devices. It is important that the damper be able to absorb shock and dissipate energy from forces directed at the damper from a variety of directions; however, such dampers may respond differently to forces directed from different directions. It is an important and desirable operating feature of such a damper to have the damper respond to such a variety of forces in a stable or predictable manner. Known prior spring dampers have suffered the problems of responsive instability due to nonaxial vibration, loading and deformation. Such nonaxial deformation may comprise conical twisting or rotation of the respective housing members to a different degree about the axis of the damper. Such instability is particularly enhanced where the damper is loaded to a substantially compressed state which imparts a high shear force to the elastomeric shear springs.
Another particular problem occurs where shear stress compels a spring into frictional engagement with a contiguous rigid member. The resulting friction wears away the spring to shorten its life and weaken it. In addition, such frictional engagement limits the natural deformation of the spring and affects its operation.
The present invention comprises a new and improved device which overcomes the energy absorption and frictional problems of prior dry viscous spring dampers by combining the advantageous features of a dry viscous spring damper with structural means for generally controlling deformation of the device in a nonaxial direction within predetermined limits and by providing surfaces contiguous to the strut shear springs to allow minimal abrasion between the shear spring and surfaces during deformation of the device. The subject invention is simple in design, economical to manufacture, readily adaptable to a plurality of energy dissipation uses, and provides improved shock absorption and energy dissipation.